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I have a 2002 325xi with 144000km on it, about 7 months I replaced the original battery thinking is was dead, never had it tested. 5 days ago my new battery died so I had it re-charged and tested. No issues battery is not faulty.

On Sunday I checked the voltage, everything seemed OK volt meter read between 13.5 and 14.4. Today after work my car started but barely, I did have an appointment for the dealership today to get the car diagnosed.

Went to go start my car, battery dead again. Ive been reading the forums all morning and came up with different ideas as to what the problem might be ie FSU, alternator, a short somewhere.

I do have one warning light on my dashboard, the rear right light is red and that has been on for a while. Once I turn on my lights it goes out though.

I'm hoping to get the car to the dealership tomorrow now, is there anything else that might be making the battery drain this much quicker? Any help would be greatly appreciated, thanks in advance!!!

What you should do is to unhook the ground on your battery and hook up your voltmeter between the negative terminal and ground. Probably use the milliamp scale. That should now measure a level of discharge. Now go to your fuse box, and pull each fuse, one at a time, and note any change to the level of battery drain. If something makes a good sized difference, you found what's causing your battery drainage.

It could be nothing...as in nothing more than you don't drive enough for the power you're using...those heated leather seats, the sub, the defroster and wipers...and all you do is drive 5 miles to work and back. That's theory one.

Connections on battery might be tightened but not tight...some terminals are just a little too small for our cables...might have been good enough at one point (small odds, but pull up on cable to test)

Sansho's test can tell you amount of drain, though remember some systems stay on for at least a half an hour after shutdown...it's got thinking to do I guess.

Then you start pulling all the fuses...and that light of yours stays on all the time but goes off when you start the car? Check ground fix if taillight...check loom from body to trunklid, if you mean one of the trunk lid lights...and if you can find the light, consider reverse or license plate lights...

Best not to let the negative terminal to battery post disconnect if possible. The reason for that is that if you disconnect it first it will remove power from every device. It's possible there is a device in the car that's not going back to sleep when you stop the car and removing the power completely resets it.

Instead set up your ammeter and connect it between the battery post and the terminal. Then remove the terminal from the battery post (breaking the main circuit) but keeping the ammeter connected (and then it takes over the connection measuring at the same time). That way the connection is never broken. It can be a bit tricky to do right.

Do not turn on the ignition (and definitely do not start the car) whilst the ammeter (assuming a regular sort of multimeter) is series. Even on a 10A range, it's likely the car will need more and blow the fuse at best.

Thanks guys, unfortunately the car is currently at the dealership, there going to do a system test. They were not to impressed that I have an aftermarket battery, almost like there going to put the blame on that. If they do not find the root cause then I will defiantly test each fuse.

As far as my drive to work lol yes good call dmax I do have a short drive to work but I drive regularly before work. Although some weeks yes its to and from work.

I charged up the battery last night car started fine this morning, drove to the dealership, I mentioned the rear tail light and the dashboard light associated with that. I passed on getting it checked for now as I wanna know the results of the test.

Just recieved a call from bmw and it is the resistor blower motor. Quite expensive to fix and they told me my theremostat is stuck. My car does not overheat nor does it take a long time to get to temp. I dunno if i will be doing that repair. Thanks for you help guys.

Thanks guys, unfortunately the car is currently at the dealership, there going to do a system test. They were not to impressed that I have an aftermarket battery, almost like there going to put the blame on that. If they do not find the root cause then I will defiantly test each fuse.

As far as my drive to work lol yes good call dmax I do have a short drive to work but I drive regularly before work. Although some weeks yes its to and from work.

I charged up the battery last night car started fine this morning, drove to the dealership, I mentioned the rear tail light and the dashboard light associated with that. I passed on getting it checked for now as I wanna know the results of the test.

Just recieved a call from bmw and it is the resistor blower motor. Quite expensive to fix and they told me my theremostat is stuck. My car does not overheat nor does it take a long time to get to temp. I dunno if i will be doing that repair. Thanks for you help guys.

Blower motor resistor, aka, fsr, aka a common diy...my guess is they'll want about $500 for it...think maybe under $100 part and a couple hours for noob.

I have a 2002 325xi with 144000km on it, about 7 months I replaced the original battery thinking is was dead, never had it tested. 5 days ago my new battery died so I had it re-charged and tested. No issues battery is not faulty.

On Sunday I checked the voltage, everything seemed OK volt meter read between 13.5 and 14.4. Today after work my car started but barely, I did have an appointment for the dealership today to get the car diagnosed.

Went to go start my car, battery dead again. Ive been reading the forums all morning and came up with different ideas as to what the problem might be ie FSU, alternator, a short somewhere.

I do have one warning light on my dashboard, the rear right light is red and that has been on for a while. Once I turn on my lights it goes out though.

I'm hoping to get the car to the dealership tomorrow now, is there anything else that might be making the battery drain this much quicker? Any help would be greatly appreciated, thanks in advance!!!

The Blower Motor Resistor (properly referred to as the Final Stage Resistor, or FSR) will not lead to battery draining. It will cause the fan in the Ventilation System to not function properly -- the fan speed selector will not work right, often causing only High Speed operation of the fan.

The red light that indicates a tail/brake light error is problematic though. You have a bad ground that needs fixing. Remove the tail lamp assembly look inside of the connectors, both on the car-side and on the lamp housing-side. On the car side of the connector, one of the pins has a BRN wire going to it, check that this pin is not burned off on either side of the connector.

You're posting from the Great White North, where the average daily temps are 3 million degrees below zero at this time of year. This is a very harsh environment for a battery, and if your battery is a Cheap Street battery, then I'd have to wonder if it is any good. I know you said it tested okay, but it sounds like it is objecting to the cold weather.

Did swapping the FSR fix your problem? I have the same exact problem and even after replacing the FSR I still have to jump my car everytime I need to start it up (2x's today even after I replaced the FSR last night)

Did swapping the FSR fix your problem? I have the same exact problem and even after replacing the FSR I still have to jump my car everytime I need to start it up (2x's today even after I replaced the FSR last night)

Did you check your battery voltage?

Might be battery, and it might just mean you're not driving long enough, or taking a lot of short trips...and have a really loud stereo. (If so, drive for 20 mins. on the highway to charge up battery and go from there...doesn't seem like it, but starting is a huge drain on battery and I think many here replace batteries when all they need to do is drive more.)

Could be alt, but you're not getting any warning lights, I presume, but check its voltage also...along with other things that could hamper the alt--corroded terminals on bat or under hood; bad grounds; bad pulleys/belts, and the incredibly rare, improper installed belt.

What you should do is to unhook the ground on your battery and hook up your voltmeter between the negative terminal and ground. Probably use the milliamp scale. That should now measure a level of discharge. Now go to your fuse box, and pull each fuse, one at a time, and note any change to the level of battery drain. If something makes a good sized difference, you found what's causing your battery drainage.

yes... but be sure to disconnect the trunk lights, as these will draw voltage since your trunk is open and throw off your readings

Might be battery, and it might just mean you're not driving long enough, or taking a lot of short trips...and have a really loud stereo. (If so, drive for 20 mins. on the highway to charge up battery and go from there...doesn't seem like it, but starting is a huge drain on battery and I think many here replace batteries when all they need to do is drive more.)

Could be alt, but you're not getting any warning lights, I presume, but check its voltage also...along with other things that could hamper the alt--corroded terminals on bat or under hood; bad grounds; bad pulleys/belts, and the incredibly rare, improper installed belt.

- I checked my battery with a MM last night and it reads at 12.7v just sitting, no trunk lights

- I drive 17 mi. each way to work (not sure if that's considered short?)

- I do have an in-line converter for an aftermarket subwoofer + amp, however, the radio must be on to power the system (remote control wire) and this setup was working fine for about month prior to the drainage

- Battery is less than 2 years old, clean as can be

- No warning lights but how do I test the ALT with a multimeter?

- Belts will be changed this weekend with a new cooling system, but can you explain how the belts play in?

The Blower Motor Resistor (properly referred to as the Final Stage Resistor, or FSR) will not lead to battery draining. It will cause the fan in the Ventilation System to not function properly -- the fan speed selector will not work right, often causing only High Speed operation of the fan.

The red light that indicates a tail/brake light error is problematic though. You have a bad ground that needs fixing. Remove the tail lamp assembly look inside of the connectors, both on the car-side and on the lamp housing-side. On the car side of the connector, one of the pins has a BRN wire going to it, check that this pin is not burned off on either side of the connector.

You're posting from the Great White North, where the average daily temps are 3 million degrees below zero at this time of year. This is a very harsh environment for a battery, and if your battery is a Cheap Street battery, then I'd have to wonder if it is any good. I know you said it tested okay, but it sounds like it is objecting to the cold weather.

Umm final stage resisters DEFINITIVELY CAN CAUSE A DRAW!!! They stick on and cause the blower motor to turn on and can run a battery down quickly.

Quick alternator test would be to start the car and then disconnect the battery. If car stays on, alternator is ok.
Could have bad contacts at the battery, alternator, or ground points.
Final stage could be stuck.

Quick alternator test would be to start the car and then disconnect the battery. If car stays on, alternator is ok.
Could have bad contacts at the battery, alternator, or ground points.
Final stage could be stuck.

NEVER DO THIS on a modern car. You could Damage the computers. That trick is for old Domestic cars......

Umm final stage resisters DEFINITIVELY CAN CAUSE A DRAW!!! They stick on and cause the blower motor to turn on and can run a battery down quickly.

I just changed out the FSR 2 days ago and although it fixed my blower speeds, I am still not getting a charge despite driving 17 mi. at a time (about 20 min.)

Quote:

Originally Posted by xavi330i

Quick alternator test would be to start the car and then disconnect the battery. If car stays on, alternator is ok.
Could have bad contacts at the battery, alternator, or ground points.
Final stage could be stuck.

I may try this, but if my car is running fine while on (no lights, no loss in power) would it still be the alternator? How often do they go out? How can I check the voltage

I just changed out the FSR 2 days ago and although it fixed my blower speeds, I am still not getting a charge despite driving 17 mi. at a time (about 20 min.)

I may try this, but if my car is running fine while on (no lights, no loss in power) would it still be the alternator? How often do they go out? How can I check the voltage

I had an eclipse that I ran for two weeks (deep cycle batt) without the alternator connected. I had no lights on the dash until the battery reached a level low enough to trigger a low voltage lamp, then eventually it would not have enough power to turn over the engine. Not all cars respond this way. Usually if the alternator is faulted, the car will draw it's power from the battery and drain it.